The voluntary recall on Tuesday of 14 of its brands in New South Wales and Australian Capital Territory was announced after tests showed variable low levels of the bacteria. "Retention samples indicated low but inconsistent levels so we sent them outside for further testing. When results came back they were still inconclusive but we decided to pull the whole lot just to be safe," said spokesman Ian Greenshields. E. coli can be fatal but typically causes abdominal pain, cramps and diarrhoea. A recent outbreak of E. coli from contaminated packaged spinach in the US led to 183 cases of illness and one death. But when contamination is at low levels in a test sample, the bacteria may not occur in every batch of product, leading to inconsistent results and making it difficult to assess the risk. However food companies are increasingly cautious about microbiological contamination. The Food Standards Australia New Zealand said this is the second most common reason for a product recall, after mislabelling. "It is a growing trend and we commend them [food companies] for that," said Lydia Buchtman, spokeswoman for the agency. National Foods says the product contamination likely happened in the plant during manufacturing but the exact source is still being investigated. Pasteurisation is designed to kill this kind of bacteria. It is not yet known how much the recall will cost the company but Greenshields said it involved 'a whole day's supply, a lot of product'. It included Pura whole milk, Pura Light Start and Woolworths and Homebrand whole milk which were manufactured on November 24 and have a best-used-before date of December 13. Earlier this week Nestlé Australia also launched a voluntary recall of its Nan 2 HA Gold infant formula in 900g cans following the discovery of metal fragments in some cans. It is believed the contamination occurred during the production process.